<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        html {
            font-size: 10px;
        }
        
        @media screen and (max-width:320px) {
            html {
                font-size: 8.53px
            }
        }
        
        @media screen and (min-width:320px) {
            html {
                font-size: 8.53px
            }
        }
        
        @media screen and (min-width:375px) {
            html {
                font-size: 10px;
            }
        }
        
        @media screen and (min-width:414px) {
            html {
                font-size: 11.04px;
            }
        }
        
        @media screen and (min-width:768px) {
            html {
                font-size: 20.48px;
            }
        }
        
        .box {
            width: 37.5rem;
            height: 37.5rem;
            background-color: skyblue;
        }
        
        .con {
            width: 37.5rem;
            height: 37.5rem;
            background-color: pink;
        }
    </style>
</head>

<body>
    <!-- rem vh vm  -->

    <div class="box"></div>
    <div class="con"></div>

</body>

</html>